The present invention generally relates to a sheet feeder, which can be used in an envelope inserting machine or the like, and, more particularly, to a sheet feeder for feeding sheets from a vertical stack.
In an inserting machine for mass mailing, there is a gathering section where enclosure material is gathered before it is inserted into an envelope at an envelope insertion area. The gathering section is sometimes referred to as a chassis subsystem, which includes a gathering transport with pusher fingers rigidly attached to a conveyor belt and a plurality of enclosure feeders mounted above the transport. If the enclosure material contains many documents, these documents must be separately fed from different enclosure feeders.
Inserting machines are well-known. For example, U.S. Pat. No. 4,501,417 (Foster et al.) discloses an inserter feeder assembly for feeding enclosures; U.S. Pat. No. 4,753,429 (Irvine et al.) discloses a collating station; and U.S. Pat. No. 5,660,030 (Auerbach et al.) discloses an envelope inserter station, wherein envelopes are separately provided to an envelope supporting deck where envelopes are spread open so as to allow enclosure materials to be stuffed into the envelopes.
An exemplar inserting machine is shown in FIG. 1. As shown, an inserting machine 10 typically includes an envelope feeder/inserter station 12 and a plurality of enclosure feeders 20. The envelope feeder/inserter station 12 includes an envelope feeder 14 above an envelope insertion area 16. Documents 22 are separately released from the enclosure feeders 20 onto a long deck 30 and collated as the released documents (not shown) are pushed by a plurality of pusher fingers 32 driven by one or more endless belts or chains 34 toward the envelope feeder/inserter station 12. At the same time, a stack of envelopes 18 are placed on the envelope feeder 14 so that one envelope at a time is released from the envelope feeder 14 into the envelope insertion area 16 where the envelope is spread open to allow the collated documents to be stuffed into the envelope. Typically the enclosure feeders are fixedly mounted to inserting machine 10 above the deck 30. As shown, the enclosure feeder 20 has a slant tray 24 for supporting the documents 22 to be released. This type of slant tray design has a very limited capacity for stacking the documents 22, partly due to the fixed distance between adjacent enclosure feeders 20. Slant trays are widely used in envelope inserting machines, as can be seen in earlier mentioned U.S. Pat. Nos. 4,501,417 (Foster et al.), 4,753,429 (Irvine et al.) and 5,660,030 (Auerbach et al.). U.S. Pat. No. 5,120,043 (Mazullo) also discloses an enclosure feeder with a slant tray for supporting the documents. U.S. Pat. No. 4,817,368 (DePasquale et al.) discloses a mailing inserting and collating apparatus, wherein a plurality of envelope hoppers each containing a vertical stack of mailing inserts for releasing the inserts into a plurality of opened envelopes. Under each envelope hopper, a rubber kicker roller having an arcuate outer surface, along with a vacuum port, is used to retrieve the lowermost insert from the stack. The major advantage of the vertical stack is that it can support more inserts or documents to be released. The major disadvantage is that the weight of the vertical stack imposes a burden to the retrieving mechanism. The weight may cause an incomplete retrieval of inserts or a torn sheet.
Thus, it is advantageous and desirable to provide a method and apparatus for reducing the burden in retrieving a lowermost sheet from a vertical stack of sheets due to the weight of the stack.
It is the primary object of the present invention to reduce the burden in retrieving a lowermost sheet from a vertical stack of sheets in a sheet feeder or the like. In particular, the burden is mostly due to the weight of the stack.
Accordingly, the first aspect of the present invention is a method of reducing the burden in retrieving sheets from the bottom of a stack of sheets of material in a sheet feeder, wherein the stack has a downward vertical force associated with gravity and the burden is related to the downward vertical force, and wherein the stack has a first side and an opposing second side, and the stack is caused to move downward toward the bottom due to the retrieving. The method comprises the steps of providing a first counteracting surface in the lower portion of the stack protruding into the first side of the stack for pushing the sheets in a first portion of the stack toward the second side, and providing a second counteracting surface on the second side below the first counteracting surface for pushing the sheets in a second portion of the stack below the first portion of the stack toward the first side, wherein the first counteracting surface provides a first counteracting force resisting the downward movement of the stack on the first side and the second counteracting surface provides a second counteracting force resisting the downward movement of the stack on the second side, and wherein the first reaction force and the second reaction force comprise upward vertical components for partially countering the downward vertical force.
Preferably, the first counteracting surface comprises a convex surface.
Preferably, the convex surface is part of a circumference of a roller, which is caused to turn by the downward movement of the stack on the first side.
Preferably, the second counteracting surface comprises a further convex surface.
It is possible that the further convex surface is part of a circumference of another roller.
It is also possible that the further convex surface is part of a large surface, which includes a concave section.
The second aspect of the present invention is an apparatus for reducing burden in retrieving sheets from bottom of a stack of sheets in a sheet feeder, wherein the stack has a downward vertical force associated with gravity and the burden is related to the downward vertical force, and wherein the stack has a first side and an opposing second side, and the stack is caused to move downward toward the bottom due to the retrieving. The apparatus comprises a first counteracting surface in the lower portion of the stack protruding into the first side of the stack for pushing the sheets in a first portion of the stack toward the second side, and a second counteracting surface on the second side below the first counteracting surface for pushing the sheets in a second portion of the stack below the first portion of the stack toward the first side, wherein the first counteracting surface provides a first counteracting force resisting the downward movement of the stack on the first side and the second counteracting surface provides a second counteracting force resisting the downward movement of the stack on the second side, and wherein the first reaction force and the second reaction force comprise upward vertical components for partially countering the downward vertical force.
The third aspect of the present invention is a sheet feeder for feeding a substantially vertical stack of sheets, wherein the stack has a bottom, a first side and an opposing second side. The sheet feeder comprises a retrieving mechanism for retrieving sheets from the bottom of the stack; a first counteracting surface in the lower portion of the stack protruding into the first side of the stack for pushing the sheets in a first portion of the stack toward the second side; and a second counteracting surface on the second side below the first counteracting surface for pushing the sheets in a second portion of the stack below the first portion of the stack toward the first side, wherein the stack is caused to move downward toward the bottom due to the retrieving, and the first counteracting surface provides a first countering acting force resisting the downward movement of the stack on the first side and the second counteracting surface provides a second countering action force resisting the downward movement of the stack on the second side results in a second reaction force from the second counteracting surface, and wherein the first counteracting force and the second counteracting force comprise upward vertical components for partially countering a downward vertical force associated with the weight of the stack.
The present invention will become apparent upon reading the description taken in conjunction with FIGS. 2 to 5b.